Impedance-changing device



Aug. 17 1926.

A. J. EAVES IMPEDANCE CHANGING DEVICE Filed August 9, 1923 F/gj men/0r:

A 905/ s .Em/es K m y :Patented an l-1,1926.

UNITED STATES PATENT OFFICE.

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This invention relates to artificial lines and more particularly to artificial line adjusting devices for controlling a plurality of impedance elements. An object of the invention is the provision of an impedance varying device which is single and efiicient and which may be operat in a facile and expeditious manner to balance the impedance of a transmission line. According to the preferred form, the in vention provides an impedance adjusting device which comprises a switch for varying the resistance, and means for varying the" electrostatic capacity in an artificial line. The switch consists of a plurality of equally spaced banks of contacts with a contact arm for each bank arranged to engage v the contacts for progressively changin t e pedance in a circuit, in the order oithe 2o arrangement of the banks of contact. Each bank of contacts is staggered with respect to-the other banks of contacts so that the contacts in the banks will be engaged'by the contact arms with respect to the contacts inthe other banks successively, thereby increasing the total number of possible changes in the associated resistance, for one complete rotation.

In the drawing, Fig. 1 illustrates a switch-. ing device of the invention partly in crosssection; Fig. 2 a sectional view taken along the broken' line 2-2'of Fig. 1; and Fig. 3 illustratesthe invention as applied to a duplex telegraph system.

Abetter understandin of the invention may be had from the fo owing description, taken in conjunction with the accompanying drawing, wherein one embodiment of the invention'is illustrated. V

Referring now for the moment to a switching device is shownwhich comprises a plurality of circular blocks of micarta, or ot er suitable insulating material, 5, 6 and 7, which have, asshown inFig. 2, a plurality of equally spaced apertures 8. Through these apertures extend clamping bolts 9, 10 and 11, which serve to securely hold the various circular blocks in position to the panel or other supporting means 12.

50 In order that the circular blocks will be spaced properly, sleeves 13 surroundin the bolts 9, 10,and'11 between the panel and the block' 5 and between the other blocks are provided. Thus, by drawing down the nuts individual to the clamping bolts, the switch provided, each of the collars being fixedly .-secured in any suitable manner to one of the adjacent sections of the shaft structure may {be securely clamped in lace. Each of the circular blocks 5, 6 and i also has a central aperture through which a ro-' tatable shaft 16 extends. This shaft 16 is divided into a plurality of sections, one individual to each of the circular blocks 5, 6

and 7. For securing the respective sections of the shaft to one another, collars 17 are and arranged to lock itself to the other of the ad- 'acent sections by means of suitable ke s 14. Also secured to the shaft 16 is a di and knob 18 serving as a means forrotating the shaft. 1

Rigidly fastened on each section of the shaft are U-shaped contact arms 19 which f are made up 'of a plurality of fiat springs and which are held in position by means of clamping nut-.20. One end of the contact arm 19 engages the flat surface of a plurality of Lr-sha'ped contact pieces 21. which, as shown in Fig. 2, are equally spaced in. the blocks 5, 6 and 7; The other end of the contact arm 19 rests on a hub 22 of conduct ing material, which has a terminal 23 serving as a connecting means for the next section of the resistance. These brushes are of such width as to bridge two adjacent contact pieces on their respectively amiated blocks before an existing connection with a contact is opened, the purpose of this arrangement being to maintain a continuous connection duringthe rotation of the brushes.

It is to be noted that in each of the circular blocks 5, 6 and 7 the sets of apertures 8 are arranged equi-distant around the outside circumference and as shown in the drawing there are preferably three sets, each of which are, therefore, spaced on centers of 120. The sets consist of three apertures each and are arranged to be substantially in alignment with the corresponding sets on the three blocks, with the exception that the first aperture of any set in block 5 is in perfect alignment with the second aperture of its corresponding set in block 6 and with the third aperture of its corresponding set in block 7 and are securely held in their respective relative positions by the bolts 9, 10 and 11. This arrangement provides a means for successively varying the resistance in the artificial line in the order of the positions of the blocks: Thus, inasmuch as the contact segments 21 are equally spacedin their respective blocks and the contact arms 19 bear the same angular position, engagement thereof with the conducting segments will be such that when the brush on block 5 is centered on a contact, as shown in Fig. 3 of the drawing, the brush on block 6 will span the contact corresponding to that in engagement on block 5 and the succeeding contact, and the brush on block 7 will be centered on the contact corresponding to the said succeeding contact on block 6 or what is designated onblock 5 as 21. It is'thus seen that such a switching device makes it possible to combine in a single unit, switch structures which may be operated from a common element successively. By having eleven conducting segments in each bank and there being three banks in the case illustrated, the number of sgeps for a complete rotation will be thirtyt ree.

Referring now to Fig. 3, there is shown' a' an artificial line, which consists of a luralj ity of resistances 30, 31 and 32, a reslstance 33 and two variable condensers 34 and 35; As is customary in duplex signaling resistance 33 and condenser 34 seem to balance the nearby portions of the line. Each of the resistances 30, 31 and 32 is connected to a. contact segment 21 individual to the circular blocks 5, 6 and 7. As shown in this figure the contact arm 19 for the contacts arrange in the circular block 5 is in engagement with segment 21', while the contact arm 19 individual to the circular block 6 is bridging the correspondingsegment with the succeeding one or that corresponding to 21" on block 5, While the contact arm. 19 for the block 7 is ee'nteredonthe contact corresponding to 21. It isthusapparent that the present invention provides a switching device whereby for a singlemovement theresistance may be varied in steps successivelyaa It is to be un derstood, however, that the artificial line comprisesnapluralityof such resistances, the resistances for the' other stepsv being of either higher orsmaller values to give the required ad ustment, Thecondenser 35 is connected between the resistances for the sections '5 and 6 and so connected that this condenser whichbalances the more distant capacity of the line is always at one third of the resistance-connected in the circuit, thus giving} more accurate adjustment; Also'as the res sistance is increased the distance which the condenser 35 is from the line is automatically memes Although the invention has been disclosed and described with reference to. a particular type of system, it is obvious that modifications may be made without departing from the spirit and scope of the present invention.

The invention claimed is:

1. In an impedance chan ing device, aplurality of banks of impe ance elements, and means for changing the impedance successively in the order of the arrangement of the banks.

2. In an impedance changing device, a plurality of banks of resistance elements, a capacity element located at approximately one-third the total resistance, and means for changing the resistance successively in the order of the banks and automatically maintaining the position of the capacity element at approximately one-third of the total resistance.

3. In an impedance cha "g'ing device, a plurality of banks of e ually spaced conducting segments, each 0 said banks being disposed on an ofi'set with respect to the other banks, impedance elements connected to said conducting segments, and means for successively engaging the segments in each of the banks for successively chang ng the the capacity elements. I

5. An artificial line simulating the im-.

pedance of an actual loaded. line, an impedance changing device in said artificial line comprising a plurality of banks of resistance elements, a capacity element, and common nieans under unitary control. for varying the said resistance elements and au- ,--'tomati cally maintaining said capacity elennpedance in the order of the arrangement 0 ment located at approximately one-third of the balancing resistance.

6. An artificial line simulating the imped cc of an actual loaded line, an im- (1 cc changing device. insaid artificial e comprising a pluralityof banks of resistance elements, an adjustable capacity element, -and means for changing the resistance 'successivel in the order of the banks andautomaticahy the 'tion of the'adjustable capacity element in the artificialhne to mamtain it at approximately one-third of the total cc of the artificial line. i

7. An artificial line the charllcteristic impedance of an actual loaged line, an impedance adjusting d evice in id artificial line comprising a plurality of banks of equally spaced conducting segments arranged in a circle, each of said banks being offset with respect to the other banks sistance elements'connected to said conducting segments, an adjustable capacity ele ment, and means for successively engaging 10 the segments in each of the banks for successively changing the resistance in the order of the arrangement cf the banks of resistances and automatically shifting the position of the capacity element to maintain it at approximately one-third of the total resistance of the artificial line.

In witness whereof, I hereunto subscribe my name this 6th day of August A. D.,' 1923.

. AUGUSTUS J. EAVES. 

